O’Neill cylinder habitats are like large soda cans, only huge, over a kilometer wide and several kilometers long. The interior is terraformed and the entire cylinder is spun for light gravity. O’Neill cylinders are sometimes paired together, end to end.

Reagan cylinders are an inefficient type of O’Neill cylinder, built by hollowing a cylinder within a spinning asteroid.

Tin can habitats are small, cramped, cheap, modular boxes, typically used in early space colonization.

Torus habitats are big donuts or wheels, spun so that the outer rim has gravity. The interior spokes are zero-G.